Cesanta Mongoose up to 7.22 PPP IPv6CP src/l2_ppp.c ppp_handle_ipv6cp len buffer overflow

Summaryinfo

A vulnerability marked as critical has been reported in Cesanta Mongoose up to 7.22. The affected element is the function ppp_handle_ipv6cp of the file src/l2_ppp.c of the component PPP IPv6CP. The manipulation of the argument len leads to buffer overflow. This vulnerability is referenced as CVE-2026-63626. Remote exploitation of the attack is possible. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Cesanta Mongoose up to 7.22 and classified as critical. This issue affects the function ppp_handle_ipv6cp of the file src/l2_ppp.c of the component PPP IPv6CP. The manipulation of the argument len with an unknown input leads to a buffer overflow vulnerability. Using CWE to declare the problem leads to CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Mongoose is an embedded web server and network library. Prior to 7.23, ppp_handle_ipv6cp() in src/l2_ppp.c trusts the 16-bit IPv6CP len field without checking it against the received payload size. On a PPP or PPPoE link using MG_ENABLE_TCPIP and MG_ENABLE_IPV6, an unauthenticated adjacent peer can complete the required LCP exchange and send a short Configure-Request with an oversized length, causing ppp_tx_frame() to read beyond recv_queue.buf and write beyond tx.buf. The same length misuse can also expose adjacent heap bytes in a reply or hang the event loop through find_opt(). This issue is fixed in version 7.23.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-63626 since 07/17/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available.

Upgrading to version 7.23 eliminates this vulnerability.

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Productinfo

Vendor

• Cesanta

Name

• Mongoose

Version

• 7.0
• 7.1
• 7.2
• 7.3
• 7.4
• 7.5
• 7.6
• 7.7
• 7.8
• 7.9
• 7.10
• 7.11
• 7.12
• 7.13
• 7.14
• 7.15
• 7.16
• 7.17
• 7.18
• 7.19
• 7.20
• 7.21
• 7.22

License

• open-source

Website

• Product: https://github.com/cesanta/mongoose/

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